The present invention relates to a fluid filter for filtering the oil of an automobile or the like.
The recycling consciousness enhanced in recent years has demanded the recovery of used oil filters for classified materials even when the oil filters are disposed of. We have proposed a vehicular fluid filter shown in FIG. 9 (in Japanese Patent Application No.HEI 9-260542) as an oil filter capable of classifying and recovering a cylindrical element of filter paper from a metallic inner cylinder holder.
An element 1 is assembled in a removable manner around an inner cylinder holder 2. On the lower end of the inner cylinder holder 2, there is axially press-fitted a flange portion 3 for supporting the lower end of the element 1. An element holding plate 4 is placed on the upper element end. At the inner side of the element holding plate 4, there is formed a fitted portion 4a to be fitted on the upper end of the inner cylinder holder 2. At the outer side of the element holding plate 4, there is formed a fitted portion 4a to be fitted on the upper end of the inner cylinder holder 2. At the outer side of the element holding plate 4, there is formed a pressure portion 4b for holding the upper end of the element 1. A relief valve 6 is projection-welded to the lower face of the element holding plate 4. Between the upper face of the pressure portion 4b of the element holding plate 4 and the crest of a filter case 5, there is sandwiched a check spring 4c. This check spring 4c is projection-welded to the element holding plate 4. The force of the pressure portion 4b for holding the element is generated when the check spring 4c is bent and deformed by the abutment against the crest of the filter case 5. The element 1 is axially sandwiched at its lower end by the flange portion 3 and at its upper end by the pressure portion 4b. 
In the vehicular fluid filter of the prior art, however, the check spring 4c is projection-molded to the element holding plate 4. Therefore, the check spring 4c and the element holding plate 4 have to be made of weldable materials, but a material having a high elastic limit cannot be used for the check spring 4c. When the vehicular fluid filter is to be assembled, therefore, the height sizes of the individual parts composing the vehicular fluid filter have to be too accurate to provide a vehicular fluid filter of easy assembly.
Since the leading end of the inner cylinder holder 2 is cut sharp, on the other hand, it may be caught by the inner circumference of the element 1 when this element 1 is to be assembled with the inner cylinder holder 2 thereby to damage the inner circumference of the element 1. Therefore, this element 1 has to be carefully assembled with the inner cylinder holder 2.
Since the inner cylinder holder 2 and the flange portion 3 are composed of separate pieces, moreover, there is demanded not only the step of press-fitting the inner cylinder holder 2 axially onto the flange portion 3 but also a sizing accuracy for each part. This requires a step of forming each part highly accurately and press-fitting it so that a vehicular fluid filter of easy assembly cannot be provided.
It is, therefore, an object of the invention to provide a vehicular fluid filter of easy assembly.
According to one aspect of the invention, there is provided a fluid filter comprising: a cylindrical filter case having a lower end opened; a cylindrical element to be inserted into the filter case; an inner cylinder holder to be so assembled in the inner circumference of the element that the element can be extracted; an element holding plate fitted on the upper end of the inner cylinder holder for holding the upper end of the element; and a spring fixed on the element holding plate for urging the element holding plate elastically to the upper end of the element, wherein the element holding plate and the spring are crimpingly fixed.
Since the element holding plate and the spring are crimpingly fixed, according to this aspect, they can be jointed to each other even if they are made of different materials. Since a material having a higher elastic limit than that of the element holding plate can be freely selected for the spring, the spring can yield to prevent the plastic deformation even when the size between the upper end of the element and the filter case fluctuates. At the assembling time, therefore, the height sizes of the individual parts composing the vehicular fluid filter need not be accurate, and it is possible to provide a vehicular fluid filter of easy assembly.
According to this aspect, the spring steel is used for the check spring so that an elastic limit can be enlarged.
According to another aspect of this invention, the fluid filter further comprises a relief valve device welded to the element holding plate for acting according to the difference between the inside and outside pressures of the element, wherein the spring is crimpingly fixed at a portion different from the welded position of the relief valve device.
According to this aspect, the spring is crimpingly fixed at a portion different from the welded position of the relief valve device so that the fluid filter can be easily manufactured without being damaged at the welded portion at the crimping step.
According to another aspect of this invention, the spring includes leaf spring portions extended and protruded from the portion crimpingly fixed to the element holding plate so that the element holding plate is urged to the upper end of the element by the elastic force which is generated by bringing the warped leaf spring portions into abutment against the filter case.
According to this aspect, the element holding plate is urged by bringing the warped leaf spring portions into abutment against the filter case, so that the number of parts can be reduced.
According to this aspect, the inner cylinder holder is curved at its end portion so that the inner cylinder holder can be smoothly assembled in the inner circumference of the element without damaging the inner circumference of the element.
According to this aspect, the end portion of the inner cylinder holder is curved by folding it inward so that its structure is not complicated while enhancing the strength of the inner cylinder holder.
According to this aspect, the inner cylinder holder is molded of a synthetic resin so that its end portion can be easily curved.
According to this aspect, the end portion of the inner cylinder holder is diametrically reduced at its end portion so that it can be smoothly assembled in the inner circumference of the element without damaging the inner circumference of the element.
According to this aspect, the inner cylinder holder is molded integrally with the flange portion so that the number of parts can be reduced while eliminating the step of press-fitting the inner cylinder holder axially onto the flange portion, to facilitate the assembly and to enhance the strength of the inner cylinder holder by the flange portion.
According to another aspect of this invention, there is provided a fluid filter comprising an inner cylinder holder to be so assembled with the inner circumference of an element that the element can be extracted, wherein the fluid filter further comprises: a plate member arranged on the side of the end portion of the inner cylinder holder; and a packing sandwiched between the end portion of the inner cylinder holder and the plate member for establishing a seal between the end portion of the inner cylinder holder and the plate member, and wherein the end portion of the inner cylinder holder is molded integrally with the inner cylinder holder.
According to this aspect, the number of parts can be reduced while facilitating the assembly by molding the end portion integrally with the inner cylinder holder.
According to another aspect of this invention, there is provided a fluid filter comprising an inner cylinder holder to be so assembled with the inner circumference of an element that the element can be extracted, wherein the outer circumference of the inner cylinder holder, as confronting the inner circumference of the element, is formed in uneven shape and has openings formed at the places other than the ridges of the outer circumference for providing communication between the inside and outside of the inner cylinder holder.
According to this aspect, the inner circumference of the element is contacted only by the ridges formed on the outer circumference of the inner cylinder holder so that the inner cylinder holder can be easily assembled with little resistance. As a result, the open area of the inner circumference of the element can be substantially enlarged to reduce the flow resistance and lower the flow velocity at the openings thereby to improve the filtering efficiency.
According to another aspect of this invention, there is provided a fluid filter comprising: a cylindrical element; an inner cylinder holder to be so assembled in the inner circumference of the element that the element can be extracted; an element holding plate fitted on the end portion of the inner cylinder holder for holding the upper end of the element; and a relief valve device attached to the element holding plate for acting according to the difference between the inner and outer pressures of the element, wherein said relief valve device is arranged in the inner circumference of the element so that it can be used as a guide for inserting the relief valve device into the inner cylinder holder by bringing the inner circumference of the inner cylinder holder into abutment against the outer circumference of the relief valve device.
According to this aspect, when the inner cylinder holder is to be inserted into the element, the relief valve device can be utilized as a guide for inserting the inner cylinder holder thereby to smoothen the assembly.
According to another aspect of this invention, there is provided a fluid filter comprising: a cylindrical element; an inner cylinder holder to be so assembled in the inner circumference of the element that the element can be extracted; an element holding plate fitted on the end portion of the inner cylinder holder for holding the upper end of the element; and a relief valve device attached to the element holding plate for acting according to the difference between the inner and outer pressures of the element, wherein said relief valve device is arranged in the inner circumference of the element so that it can regulate the position of the inner cylinder holder for assembling the relief valve device into the inner cylinder holder by bringing the inner circumference of the inner cylinder holder into abutment against the outer circumference of the relief valve device.
According to this aspect, when the inner cylinder holder is assembled into the element, the relief valve device can be utilized as a member for positioning the inner cylinder holder thereby to improve the assembling accuracy.
According to another aspect of this invention, the crimped portion on the holding plate is crimpingly fixed on the spring.
According to this aspect, the crimped portion is crimped on the holding plate so that the yield of the spring can be improved (better than the case where the crimped portion is formed on the spring side). Even if a material having a higher elastic limit than that of the holding plate is freely selected for the spring, moreover, the crimping works can be facilitated to retain the crimping accuracy.